The invention relates to a device and to a process for determining respiratory phases of the sleep of a user.
Respiratory disorders of sleep, such as the Sleep Apnea Syndrome (SAS) are characterized, in general, by a disfunctioning of the respiratory function during sleep.
Considerable fragmentation of sleep is observed in subjects affected by such a syndrome, with short phases of sleep and the resumption of normal respiration usually accompanied by a brief period of wakefulness, lasting a few seconds.
The normal course of sleep, from the stage of light sleep to the stage of deep sleep, via a stage of paradoxical sleep, is greatly disturbed, this having consequences on the daytime routine of these subjects. Thus, they tend to be drowsy, or even to fall asleep when fully active, and a decrease in intellectual and sexual functions is also observed in them, together with the risks of hypertension and cardiac insufficiency.
Respiratory disorders may be of the obstructive or central type.
In the first case, a total obstruction (obstructive apnea) or partial obstruction (obstructive hypopnea) of the upper airways is observed while muscular effort is maintained. Disorders of this type are often associated with considerable snoring.
In the second case, muscle control is absent (central apnea) or diminished (central hypopneal), the upper airways being open.
Obstructive disorders represent the great majority of nocturnal respiratory disorders.
Customarily, diagnosis of respiratory sleep disorders is performed in a sleep laboratory by recording and studying numerous parameters related:
either to sleep; electroencephalogram, electroocculogram, electromyogram,
or to cardio-respiratory function: electrocardiogram, respiratory frequency, nasal and/or buccal flow, thoracic and abdominal movements, arterial oxygen saturation, snoring.
Diagnosis of these sleep pathologies is recent and its implementation is unwieldy and requires that the subject be hospitalized for one or two nights.
The treatment of respiratory sleep disorders customarily employs an appliance for keeping the upper airways open.
This appliance usually comprises a mask-based positive pressure apparatus (CPAP), in which a means of compressing the ambient air, operated by a control device, delivers air pressure to a pipe and then to a mask placed on the patient""s nose in a leaktight manner.
The control device compares the value of the pressure in the mask with a set pressure target value and, depending on the deviation measured, adjusts a control signal which it delivers to the means for compressing the ambient air.
At present, the pressure target value to be applied in the mask of the patient is determined empirically in the sleep laboratory by progressively increasing an initial target value and observing the consequences for the respiratory disorders, the value chosen being the first value for which normal unfragmented sleep is observed.
There are apparatuses for diagnosing or/and treating these nocturnal respiratory disorders, which detect apneas or hypopneas, but do not differentiate between central and obstructive events.
Others, after having detected an apnea, send a pressure pulse to the patient""s mask and study any echo: if there is no echo, the event is central, and if an echo returns, the event is obstructive.
Such apparatuses are described in particular in the documents FR-A-2663547 and FR-A-2674133.
However, in order to be able to establish a correct diagnosis of respiratory disorders (apneas, hypopneas, pathology of increased resistance, etc.) and/or to determine and/or initiate adequate and effective treatment, it may be necessary or even vital for the practitioner, that is to say the doctor or the like, to have a reliable image representative of the succession of the various inhalatory and exhalatory phases of his patient, that is to say the image of the subject""s respiratory flow or rate of flow.
However, existing processes and apparatuses do not allow this kind of reliable and accurate determination of the image of the said respiratory rate of flow.
Henceforth, it is readily understood that diagnosis and/or subsequent treatment may be incorrect or incomplete.
The aims of the present invention are therefore to propose a process and an apparatus for diagnosing and/or treating respiratory sleep disorders:
which are able to allow the reliable and accurate determination, from various respiration parameters for a patient, of the latter""s various respiratory phases,
which are able to determine accurately the phases of snoring and/or phenomena with a partial obstruction of the patient""s respiratory passages,
which can be used both in a sleep laboratory, that is to say in a hospital environment, and also at the patient""s home, and
which have a reasonable cost.
To this end, the subject of the invention is a device for determining respiratory phases of the sleep of a user, comprising means for measuring at least two physical variables of which at least a first physical variable is representative of the nasal flow of the user and of which at least a second physical variable is representative of the user""s buccal flow, characterized in that it furthermore comprises means for processing and converting each physical variable with a view to establishing its degree of membership in at least one state of a fuzzy variable, and means for applying pre-established rules between at least one state of a first fuzzy variable and a state of a second fuzzy variable so as to evaluate the degree of membership in a respiratory phase state of the sleep of the user according to fuzzy logic.
The device according to the invention can additionally comprise one or more of the following characteristics:
each fuzzy variable possesses at least two states,
the states of respiratory phases of sleep comprise at least one state of normal respiration, a state of apnea and a state of hypopnea,
the degrees of membership of the states associated with a fuzzy variable are established on the basis of continuous curves defined over the entire universe of discourse of a measured physical variable,
the measurement means comprise a pressure sensor linked to a nose piece intended to be worn by the user and one of the measured physical variables is the pressure signal measured by the said pressure sensor,
the processing and conversion means comprise means for extracting from the measured pressure signal snoring phases associated with breathing-obstruction phenomena,
the means for extracting snoring phases comprise means of high-pass filtering of the pressure signal, means for amplifying the filtered signal, means for interpolating the amplified filtered signal so as to obtain an envelope curve, means for storing a reference curve and means for comparing the envelope curve with the reference curve so as to determine the presence of snoring phases,
the measurement means comprise a current sensor measuring the current consumed by a low-inertia turbine which is linked to the nose piece and one of the measured physical variables is the current consumed by the turbine,
the processing and conversion means comprise means for extracting from the signal of current consumed an image of the nasal flow of the user, means for determining the phases of nasal inhalation and exhalation of the user, means for calculating the time derivative of the amplitude of the nasal flow during an inhalation phase and means for utilizing the derivative so as to determine whether the user is or is not suffering from a partial obstructive phenomenon,
the means for utilizing the derivative of the amplitude of the nasal flow comprise means for comparing the absolute value of the derivative with at least one reference value and means for measuring the duration for which the absolute value of the derivative is less than the at least one reference value,
the means for utilizing the derivative furthermore comprise means for charting the number of changes of sign of the derivative when the latter is less than the reference value,
the measurement means comprise a member for measuring the resistance of a thermistor intended to be placed in proximity to the mouth of the user, and one of the measured physical variables is the resistance measured by the member for measuring the resistance of the thermistor.
The subject of the invention is also a process for determining respiratory phases of the sleep of a user, characterized in that it comprises the following steps:
at least two physical variables are measured, of which at least a first physical variable is representative of the nasal flow of the user and of which at least a second physical variable is representative of the user""s buccal flow,
each physical variable is processed and converted with a view to establishing its degree of membership in at least one state of a fuzzy variable, and
pre-established rules between at least one state of a first fuzzy variable and a state of a second fuzzy variable are applied so as to evaluate the degree of membership in a respiratory phase state of the sleep of the user according to fuzzy logic.
This process can moreover comprise one or more of the following characteristics:
each fuzzy variable possesses at least two states,
the states of respiratory phases of sleep comprise at least one state of normal respiration, a state of apnea and a state of hypopnea,
the degrees of membership of the states associated with a fuzzy variable are established on the basis of continuous curves defined over the entire universe of discourse of a measured physical variable,
one of the measured physical variables is the pressure in a nose piece worn by the user,
during the processing and conversion, snoring phases associated with breathing-obstruction phenomena are extracted from the measured pressure signal,
during extraction, high-pass filtering of the pressure signal is carried out, the filtered signal is amplified, the amplified filtered signal is interpolated so as to obtain an envelope curve, and the envelope curve is compared with a reference curve so as to determine the presence of snoring phases,
to obtain an image of the nasal flow, the current consumed by a low-inertia turbine which is linked to the nose piece worn by the user is for example measured,
during extraction of the image of the nasal flow, the phases of inhalation and exhalation of the user are determined and the time derivative of the amplitude of the nasal flow during an inhalation phase is calculated and this derivative thus calculated is utilized to determine whether or not the user is suffering from a partial obstructive phenomenon,
during utilization of the derivative of the amplitude of the nasal flow, the absolute value of this derivative is compared with at least one reference value, and the duration for which the absolute value of the derivative is less than the said at least one reference value is measured,
during utilization of the derivative of the amplitude of the nasal flow, the number of changes of sign of the derivative when the absolute value of the latter is less than the at least one reference value is moreover charted,
to obtain an image of the buccal flow, the resistance of a thermistor placed in proximity to the said user""s mouth is for example measured.
The subject of the invention is also a method for diagnosing the respiratory phases of the sleep of a patient suffering from respiratory sleep disorders, in particular sleep apnea, characterized in that it comprises the following steps:
at least two physical variables are measured, of which at least a first physical variable is representative of the nasal flow of the user and of which at least a second physical variable is representative of the user""s buccal flow,
each physical variable is processed and converted with a view to establishing its degree of membership in at least one state of a fuzzy variable, and
pre-established rules between at least one state of a first fuzzy variable and a state of a second fuzzy variable are applied so as to evaluate the degree of membership in a respiratory phase state of the sleep of the user according to fuzzy logic.
This process can additionally comprise one or more of the following characteristics:
each fuzzy variable possesses at least two states,
the states of respiratory phases of sleep comprise at least one state of normal respiration, a state of apnea and a state of hypopnea,
the degrees of membership of the states associated with a fuzzy variable are established on the basis of continuous curves defined over the entire universe of discourse of a measured physical variable,
one of the measured physical variables is the pressure in a nose piece worn by the user,
during the processing and conversion, snoring phases associated with breathing-obstruction phenomena are extracted from the measured pressure signal,
during extraction, high-pass filtering of the pressure signal is carried out, the filtered signal is amplified, the amplified filtered signal is interpolated so as to obtain an envelope curve, and the envelope curve is compared with a reference curve so as to determine the presence of snoring phases,
to obtain an image of the nasal flow, the current consumed by a low-inertia turbine which is linked to the nose piece worn by the patient is for example measured,
during extraction of the image of the nasal flow, the phases of inhalation and exhalation of the said patient are determined and the time derivative of the amplitude of the nasal flow during an inhalation phase is calculated and this derivative thus calculated is utilized to determine whether or not the patient is suffering from a partial obstructive phenomenon,
during utilization of the derivative of the amplitude of the nasal flow, the absolute value of this derivative is compared with at least one reference value, and the duration for which the absolute value of the derivative is less than the at least one reference value is measured,
during utilization of the derivative of the amplitude of the nasal flow, the number of changes of sign of the derivative when the absolute value of the latter is less than the at least one reference value is moreover charted,
to obtain an image of the buccal flow, the resistance of a thermistor placed in proximity to the patient""s mouth is for example, measured.